1. Field of the Invention
The present invention relates to a method of producing a choline of a high purity. More specifically, the invention relates to a method of producing a choline of a high purity using, as a starting material, a molecule-inclusion complex of the choline passing through a choline carbonate and/or a choline bicarbonate.
2. Prior Art
A choline is a strongly basic substance and is used as a photoresist-developing solution. It is, however, difficult to remove by-products formed during the production of a chlorine. So far, therefore, the choline has been used in the presence of by-products thereof.
The choline is usually prepared in compliance with the following reaction formula (1), ##STR1##
This is the addition reaction in which an ethylene oxide is added to a trimethylamine, and it is estimated that the compounds of the following formula (2) are formed as by-products, ##STR2##
These by-products are the ones in which the ethylene oxides are successively added to the choline and, wherein n is chiefly 1 or 2. A conventional aqueous solution of the choline contains the above-mentioned by-products in amounts of from about 2 to about 3% by weight with respect to the choline.
The present inventors have already proposed a method by which a quaternary ammonium hydroxide and/or a salt thereof forms an inclusion complex with particular phenols (Japanese Patent Application No. 38894/1994) and a method by which choline, too, forms a similar molecule-inclusion complex which reacts with a carbon dioxide gas to form a choline carbonate and/or a choline bicarbonate (Japanese Patent Application No. 255760/1994 ).
It is virtually difficult to suppress the formation of, or to remove, by-products contained in the choline relying upon a generally employed chemical or physical treatment such as improving the reaction conditions for the choline, distillation, recrystallization or adsorption. If a highly pure choline could be produced without containing by-products, a further extended application is expected as a photoresist-developing solution and, besides, new applications can be explored in the fields of medicine, agricultural chemicals and functional materials.